Neurons extend dendrites and axons to receive and send signals. If either type of process is removed, the cell cannot function. Rather than undergoing cell death, some neurons can regrow axons and dendrites. Axon and dendrite regeneration have been examined separately and require sensing the injury and reinitiating the correct growth program. Whether neurons in vivo can sense and respond to simultaneous axon and dendrite injury with polarized regeneration has not been explored. To investigate the outcome of simultaneous axon and dendrite damage, we used a Drosophila model system in which neuronal polarity, axon regeneration, and dendrite regeneration have been characterized. After removal of the axon and all but one dendrite, the remaining dendrite was converted to a process that had a long unbranched region that extended over long distances and a region where shorter branched processes were added. These observations suggested axons and dendrites could regrow at the same time. To further test the capacity of neurons to implement polarized regeneration after axon and dendrite damage, we removed all neurites from mature neurons. In this case a long unbranched neurite and short branched neurites were regrown from the stripped cell body. Moreover, the long neurite had axonal plus-end-out microtubule polarity and the shorter neurites had mixed polarity consistent with dendrite identity. The long process also accumulated endoplasmic reticulum at its tip like regenerating axons. We conclude that neurons in vivo can respond to simultaneous axon and dendrite injury by initiating growth of a new axon and new dendrites.

神经元延伸树突和轴突以接收和发送信号。如果删除了任一类型的进程，则该单元将无法运行。一些神经元不会经历细胞死亡，而是可以再生轴突和树突。轴突和树突再生已分别进行了检查，需要感知损伤并重新启动正确的生长程序。尚未探索体内神经元是否可以通过极化再生感知和响应同时发生的轴突和树突损伤。为了研究同时发生的轴突和树突损伤的结果，我们使用了一个果蝇模型系统，其中神经元极性、轴突再生和树突再生已被表征。去除轴突和除一个树突外的所有树突后，剩余的枝晶转变为具有长距离延伸的长非分支区域和添加了较短分支过程的区域的过程。这些观察结果表明轴突和树突可以同时再生。为了进一步测试神经元在轴突和树突损伤后实现极化再生的能力，我们去除了成熟神经元的所有轴突。在这种情况下，从剥离的细胞体中再生出长的不分枝的神经突和短的分枝神经突。此外，长轴突具有轴突正端微管极性，较短的轴突具有与树突特征一致的混合极性。这个漫长的过程还在其尖端积累了内质网，就像再生轴突一样。